Lubricants are the excipients that are added in the formulation to prevent sticking by reducing friction between particles and machine parts. Apart from giving this effect, lubricant also affects the tablet’s disintegration and dissolution profile.
Lubricants form a layer around granules which reduces friction and there are two types of lubricants, one is hydrophobic e.g. Mg-stearate and the other is hydrophilic e.g. sodium stearyl fumarate or SFM.
What Is a Disintegration
The process where tablets or capsules break down into small fragments when they come in contact with fluid leaving behind no solid mass is known as disintegration.
Hydrophobic lubricants affect tablet disintegration. Hydrophobic means water repellant so these types of lubricants result in prolonged disintegration time & when disintegration time is prolonged the drug release from dosage form is also reduced and it results in a decreased dissolution profile.
The issue of prolonged disintegration is observed in the following 2 conditions
- Excessive Concentration
- Prolonged Mixing Time
If the concentration of hydrophobic lubricants exceeds the recommended limits or the mixing time is increased then we observe the defect of prolonged disintegration.
How Does It Affect?
As we discussed previously the lubricants form a layer around granules to prevent sticking and to ensure smooth ejection of tablets from dies. In optimum conditions, this layer is not very strong but if the mixing time of granules with lubricants is increased then the formed layer becomes stronger and prevents the penetration of fluid resulting in prolonged disintegration.
In the same manner, if a higher concentration of hydrophobic lubricants is used the layer formed around granules becomes more strong or thick and retard or slows down the water penetration during disintegration and increases the disintegration time.
When disintegration time is increased the dissolution profile is also prolonged. So lubricants should be used in optimum concentration and should be added at the end of blending and blending time should be minimum of 3 to 5 minutes.
Conclusion
Lubricants especially the hydrophobic lubricants retard or prolong the disintegration time so in these conditions the hydrophilic lubricants are used .The mixing time of granules with lubricants should be 3 to 5 minutes.